What kind of mileage are you folks seeing? I get about 30 right now with my highish mileage 1.6. I'm thinking of swapping in a nice 1.8 that I have. I'm wondering what the mileage would be like with the 1.6 rear end, vs using the 1.8 rear. I commute in this car, and need the mileage to stay decent. Id love to autocross more, but I need more time. Who knows what class I would be in any how, as the car is a 1994 body, with a 1990 drivetrain anyway...
Joey
The only guy I know that kept track of mileage after the swap said that he lost 2 MPG, down to 28. Quicker car though...
Keep a 1.8 rear around, as the 1.6 is of marginal strength.
mistanfo wrote: The only guy I know that kept track of mileage after the swap said that he lost 2 MPG, down to 28. Quicker car though... Keep a 1.8 rear around, as the 1.6 is of marginal strength.
Which rearend?
Joey
Is the 1.8 diff a Torsen? If so you should use the 1.6 diff and sell me the one from the 1.8 
It will get better mileage with the 1.8 rear end, 4.1:1 ration instead of 4.3:1 of the 1.6 but I don't have any exact numbers of what to expect.
EvanB wrote: Is the 1.8 diff a Torsen? If so you should use the 1.6 diff and sell me the one from the 1.8
Nope, I dont think the 1.8 is a torsen. According to mazda the only option this parts car shipped with was AC. Unless it was swapped at some point. I do have a 1.6 LSD for sale...
Joey
too many variables.
how will it be driven? any other modifications?
my thoughts are that it's gonna be negligible regardless.
belteshazzar wrote: too many variables. how will it be driven? any other modifications? my thoughts are that it's gonna be negligible regardless.
Long commute. I'm just wondering how much of a change people have noticed when they made the swap. I can extrapolate from there.
Joey
I wouldn't be worried about a 1.6 rear end with a mostly-stock 1.8. I've seen people break the little r&p with a stock 1.6, but you have to be a bit of an abuser for that. I've personally put a fair bit of abuse through them with turbo 1.6s without a problem. So while it's nice to upgrade to a 1.8 rear because of the better differential potential and the greater range of ratios, I wouldn't lose any sleep over the 1.6 rear.
Of course fuel economy will depend on driving style, but if we're comparing like-to-like: the 1990 Miata was rated at 22 city/24 highway. The 1994 was rated at 19/21. That should be a close enough comparison to give you a good idea.
The difference between the two rears is only 5%, not a massive alteration.
My NB gets 29 mpg with the stock rear end ratio of 4:10 or 4:30, I can't remember which it is.
My 99 gets 26, mostly highway driving @ ~80mph. Seems most report higher.
MattGent wrote: My 99 gets 26, mostly highway driving @ ~80mph. Seems most report higher.
At 80mph? I doubt it, unless they swapped a 3.63 rear end or something. That motor is screaming at 80mph.
I get like... 23mpg highway out of my NB, but i'm not sure i count. Either way, still sucks.
Wow. My 1.6 gets about 30 at 80 or so. And its SCREAMING!
Joey
joey48442 wrote: Wow. My 1.6 gets about 30 at 80 or so. And its SCREAMING! Joey
80mph is about 4000rpms for me, if that helps at all?
But this is why i'm not sure it's so relevant. I've got a 6spd with a 4.10, and most people report better MPG than mine.
I'll have to check mine on a nice long Interstate run now. At 80 mine spins about 4300 RPM , I think. Which versions have a 3.63 ?
No US cars have a 3.63.
1990-93 4.30
1994-97 4.10
1999-03 5-speed 4.3
1999-03 6-speed 3.9 (but short gearing in the 'box)
2004-05 6-speed 4.1
I forget what the 2004-05 5-speeds have.
If you want to check your actual engine speed: http://flyinmiata.com/tech/gearing.php
There's a lot that can affect mileage, of course. Running a hardtop is an easy way to increase your highway mileage. But if you want apples to apples, the EPA numbers should be directly comparable.
I get about 28 mpg commuting with my hardtop on. I was around 26 mpg with the soft top.
Mine's a 96 btw.
92CelicaHalfTrac wrote:MattGent wrote: My 99 gets 26, mostly highway driving @ ~80mph. Seems most report higher.At 80mph? I doubt it, unless they swapped a 3.63 rear end or something. That motor is screaming at 80mph. I get like... 23mpg highway out of my NB, but i'm not sure i count. Either way, still sucks.
Isn't yours a Mazdaspeed? The turbo - more specifically using it a lot - can't help. ;-)
dculberson wrote:92CelicaHalfTrac wrote:Isn't yours a Mazdaspeed? The turbo - more specifically using it a lot - can't help. ;-)MattGent wrote: My 99 gets 26, mostly highway driving @ ~80mph. Seems most report higher.At 80mph? I doubt it, unless they swapped a 3.63 rear end or something. That motor is screaming at 80mph. I get like... 23mpg highway out of my NB, but i'm not sure i count. Either way, still sucks.
Yeah it's a Mazdaspeed, but i'm talking steady state cruising. I went entire tanks without boosting on the 3,000 mile trip home.
92CelicaHalfTrac wrote: Yeah it's a Mazdaspeed, but i'm talking steady state cruising. I went entire tanks without boosting on the 3,000 mile trip home.
I guess you're right - the highway mileage rating is the same for the naturally aspirated versus turbo versions. I never got below 25mpg on my 1999 Miata, and that was city or highway, driving it like a grandma or flogging the snot out of it. It just always had mid-20's fuel economy. Not that I measured it that often.
I always laugh when I see "35mpg!!" (or more) in Craigslist Miata ads. Maybe if you're cruising at 30mph in 5th gear for 3 hours straight. But not in any real world usage.
dculberson wrote:92CelicaHalfTrac wrote: Yeah it's a Mazdaspeed, but i'm talking steady state cruising. I went entire tanks without boosting on the 3,000 mile trip home.I guess you're right - the highway mileage rating is the same for the naturally aspirated versus turbo versions. I never got below 25mpg on my 1999 Miata, and that was city or highway, driving it like a grandma or flogging the snot out of it. It just always had mid-20's fuel economy. Not that I measured it that often. I always laugh when I see "35mpg!!" (or more) in Craigslist Miata ads. Maybe if you're cruising at 30mph in 5th gear for 3 hours straight. But not in any real world usage.
Pure highway, with a 1.6L, hard tires with no grip, everything working very well, and trying very hard, you absolutely can 40mpg. It's absolutely painful and totally not worth it though.
I used to be able to get about 600 km out of a 1.6 tank pretty consistently when I was commuting across Ontario. Hwy 401 is good for fuel economy, it's pretty flat with long stretches without interruption. Cruising at 120 kmh with a hardtop on and decent grippy tires and without trying but driving sensibly. That's what, 31 mpg?
If I were doing the same south of the border in the US where the limits were 55, I could see mid-30's pretty easily 
Drop in an ECU that can do closed-loop fuel tuning all the time and it'll improve - we've seen 35 highway mpg on a 350 hp Miata running on 245-series sticky tires. He wasn't trying to go for max economy, but he was running in convoy with a classic Mini at 70 mph. The Mini was getting the same fuel economy...
In reply to Keith:
What is this "km" you speak of? 
It's a socialist thing.
As long as it's not a terr'rist thing I guess we don't have anything to worry aboot.
MG Bryan wrote: As long as it's not a terr'rist thing I guess we don't have anything to worry aboot.
When we take over it will be very painless and you will feel no anxiety at all ! You have nothing to be worried about. We will assimilate you politely.
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